function of NO x (ie, NO+ NO 2). This relationship is a linchpin for top-down isoprene
emission inventory verification from orbital HCHO column observations. It is also a
benchmark for overall photochemical mechanism performance with regard to VOC
oxidation. Using a comprehensive suite of airborne in situ observations over the southeast
US, we quantify HCHO production across the urban–rural spectrum. Analysis of isoprene …